1. Field of the Invention
The invention relates to pump devices, and is directed more particularly to a gear-type pump for bulk thermoplastic materials.
2. Description of the Prior Art
In the production of man-made tow, fiber and film, the starting material, hereinafter referred to as "bulk thermoplastic material", is made fluid, as by melting, extruded through small holes or dies, and then solidified by cooling or chemical treatment. The extrusion is accomplished by the thermoplastic material being forced by a pump through a spinning jet, spinneret, die or casting head.
Pumps for forcing such materials, e.g., nylon, through spinnerets and dies are known in the art and generally comprise a gear-type pump including a housing having an inlet and outlet for the resin material, and intermeshing gears operative to drive the material through the pump and to, and through, the spinneret or dies. Such pumps currently are not provided with self-contained heating means, although it is most beneficial that the thermoplastic material be heated and not allowed to cool during transit through the pump.
In addition to the above services, similar but larger gear-type pumps are used for the mass transfer of thermoplastic and other materials from one point to another. Such pumps, generally known as transfer pumps are subject to the same benefits by the addition of heat.
To alleviate the problem, external heating means are frequently attached to, or applied to, the pumps. The results of such attachments, or outside application of heat, are lacking in uniformity at best and in many cases are, to a large degree, ineffectual or unreliable. They also serve to increase the size (bulk) of the pumps which are frequently used in highly congested areas. In such cases, the only recourse is to heavily insulate the pumps as far as possible which is not usually sufficient to maintain the fluid temperatures desired.